Om is a sacred sound, mantra and a spiritual icon. In Hinduism, Om refers to Atman (soul, self within) and Brahman (ultimate reality, entirety of the universe, truth, divine, supreme spirit, cosmic principles, knowledge) In western culture this sacred spiritual incantation is most commonly made before and during meditative and spiritual activities such as Yoga. The word om is nebulous and vague - it can mean almost anything. Like all chants, it gathers and focuses the mind, om in particular seems to calm the nervous system.